1. Field of the Invention
This invention relates to a spring adjustment mechanism for a beater of a drum pedal enabling free adjustment of the beater amplitude and the pedal height and particularly to assure that the tension on the return spring stays at a set level.
2. Description of Related Art
In a conventional beater mechanism for a bass drum as illustrated in FIGS. 1 and 2, a pair of supports 92 is erected at both sides of the base 91 of a drum pedal device 90. A beater rotary shaft 94 is rotatably supported at the top of the supports 92 through conventional bearings 93.
There is a beater mounting member 110 approximately at the center of the rotary shaft 94. Integral with the beater mounting member 110 is an operating member 120, which is in the shape of a wheel or sprocket. A beater head 115 is fixed to the beater mounting member 110 by screws 116 or other suitable fastener.
The drive member 120 comprises a sprocket or a partial sprocket, with a chain 121 having an end that is fixed at the drive member 120. The chain 121 is partially wound on the outer periphery of the drive member 120. The other end of the chain 121 is linked to a foot pedal 95. As the foot pedal 95 is pressed the chain 121 is pulled down. This rotates the drive member 120 which in turn rotates the beater, thereby causing the beater head 115 to beat the drum head surface D.
A spring 107 is tensioned to normally return the beater 115 to its original position automatically. The spring 107 is connected to the shaft 94 through a cam and hook assembly generally designated as 100 and 106.
Adjustment of the tension of the spring 107 in the above conventional device is done with an adjustment device 140 which is provided at the bottom of the spring 107. The adjustment device 140 comprises an adjustment screw 141, an adjustment nut 142 threaded on the screw 141 below the bracket 109 and a lock nut 143 threaded on the screw above the bracket 109. The adjustment screw 141 is inserted through an adjustment hole in the bracket 109 and is linked to the lower end of the spring 107. The screw is then secured from below the lower bracket 109 by the adjusting nut 142 and is locked in the selected adjusted position by tightening the lock nut 143 against the bracket 109.
For adjusting the tension of the spring 107, the lock nut 143 is loosened, and the adjusting nut 142 is rotated until the spring has a desired spring tension. Then the lock nut 143 is tightened against the lower bracket 109, thereby fixing the position of the adjustment screw 141.
In the above described mechanism of the prior art, during use of the drum pedal the adjustment nut may become loosened so that the set position of the desired spring tension is changed.